diff options
Diffstat (limited to 'libc/sysdeps/linux/x86_64/makecontext.c')
| -rw-r--r-- | libc/sysdeps/linux/x86_64/makecontext.c | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/x86_64/makecontext.c b/libc/sysdeps/linux/x86_64/makecontext.c new file mode 100644 index 000000000..54730312a --- /dev/null +++ b/libc/sysdeps/linux/x86_64/makecontext.c @@ -0,0 +1,121 @@ +/* Create new context. + Copyright (C) 2002, 2004, 2005, 2008 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Andreas Jaeger <aj@suse.de>, 2002. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include <sysdep.h> +#include <stdarg.h> +#include <stdint.h> +#include <ucontext.h> + +#include "ucontext_i.h" + +/* This implementation can handle any ARGC value but only + normal integer parameters. + makecontext sets up a stack and the registers for the + user context. The stack looks like this: + +-----------------------+ + | next context | + +-----------------------+ + | parameter 7-n | + +-----------------------+ + | trampoline address | + %rsp -> +-----------------------+ + + The registers are set up like this: + %rdi,%rsi,%rdx,%rcx,%r8,%r9: parameter 1 to 6 + %rbx : address of next context + %rsp : stack pointer. +*/ + +/* XXX: This implementation currently only handles integer arguments. + To handle long int and pointer arguments the va_arg arguments needs + to be changed to long and also the stdlib/tst-setcontext.c file needs + to be changed to pass long arguments to makecontext. */ + + +void +__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...) +{ + extern void __start_context (void); + greg_t *sp; + unsigned int idx_uc_link; + va_list ap; + int i; + + /* Generate room on stack for parameter if needed and uc_link. */ + sp = (greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp + + ucp->uc_stack.ss_size); + sp -= (argc > 6 ? argc - 6 : 0) + 1; + /* Align stack and make space for trampoline address. */ + sp = (greg_t *) ((((uintptr_t) sp) & -16L) - 8); + + idx_uc_link = (argc > 6 ? argc - 6 : 0) + 1; + + /* Setup context ucp. */ + /* Address to jump to. */ + ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t) func; + /* Setup rbx.*/ + ucp->uc_mcontext.gregs[REG_RBX] = (uintptr_t) &sp[idx_uc_link]; + ucp->uc_mcontext.gregs[REG_RSP] = (uintptr_t) sp; + + /* Setup stack. */ + sp[0] = (uintptr_t) &__start_context; + sp[idx_uc_link] = (uintptr_t) ucp->uc_link; + + va_start (ap, argc); + /* Handle arguments. + + The standard says the parameters must all be int values. This is + an historic accident and would be done differently today. For + x86-64 all integer values are passed as 64-bit values and + therefore extending the API to copy 64-bit values instead of + 32-bit ints makes sense. It does not break existing + functionality and it does not violate the standard which says + that passing non-int values means undefined behavior. */ + for (i = 0; i < argc; ++i) + switch (i) + { + case 0: + ucp->uc_mcontext.gregs[REG_RDI] = va_arg (ap, greg_t); + break; + case 1: + ucp->uc_mcontext.gregs[REG_RSI] = va_arg (ap, greg_t); + break; + case 2: + ucp->uc_mcontext.gregs[REG_RDX] = va_arg (ap, greg_t); + break; + case 3: + ucp->uc_mcontext.gregs[REG_RCX] = va_arg (ap, greg_t); + break; + case 4: + ucp->uc_mcontext.gregs[REG_R8] = va_arg (ap, greg_t); + break; + case 5: + ucp->uc_mcontext.gregs[REG_R9] = va_arg (ap, greg_t); + break; + default: + /* Put value on stack. */ + sp[i - 5] = va_arg (ap, greg_t); + break; + } + va_end (ap); + +} + + +weak_alias (__makecontext, makecontext) |